Method of manufacturing organic light emitting display device

ABSTRACT

An organic light emitting display device having high transmittance with respect to external light and a method of manufacturing the same. The organic light emitting display device includes a substrate; a plurality of pixels formed on the substrate, each of the pixels including a first region that emits light and a second region that transmits external light; a plurality of thin film transistors disposed in the first region of each pixel; a plurality of first electrodes disposed in the first region of each pixel and electrically connected to the thin film transistors, respectively; a second electrode formed opposite to the plurality of first electrodes and comprising a plurality of transmission windows corresponding to the second regions; and an organic layer formed between the first electrodes and the second electrode. The transmission windows can be formed in the second electrode, that is, a cathode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional application based on pending application Ser. No.13/038,836, filed Mar. 2, 2011, the entire contents of which is herebyincorporated by reference.

This application claims the benefit of Korean Patent Application No.10-2010-0021384, filed on Mar. 10, 2010, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND

1. Field

An aspect of the present invention relates to an organic light emittingdisplay device, and more particularly, to a transparent organic lightemitting display device and a method of manufacturing the same.

2. Description of the Related Art

As organic light emitting display devices have superior characteristicssuch as wide viewing angle, high contrast ratio, short response time,and low power consumption, they are widely used in personal portabledevices such as MP3 players, mobile phones, television sets, etc.

Also, transparent organic light emitting display devices have beenconstructed using transparent thin film transistors and transparentorganic light emitting devices.

However, since a cathode of the transparent organic light emittingdisplay device is formed of a metal, there is a limit in increasing thetransmittance of the transparent organic light emitting display device.

SUMMARY

An aspect of the present invention provides a transparent organic lightemitting display device having high transmittance with respect toexternal light and a method of manufacturing the transparent organiclight emitting display device.

According to another aspect of the present invention, there is alsoprovided an organic light emitting display device including a cathodehaving transmission windows and that are formed in a simple way, and amethod of manufacturing the organic light emitting display device.

According to an aspect of the present invention, there is provided anorganic light emitting display device including a substrate; a pluralityof pixels formed on the substrate, each of the pixels having a firstregion that emits light and a second region that transmits externallight; a plurality of thin film transistors disposed in the first regionof the pixel; a plurality of first electrodes disposed in the firstregion of the pixel and electrically connected to the thin filmtransistors, respectively; a second electrode formed opposite to theplurality of first electrodes and comprising a plurality of transmissionwindows corresponding to the second regions; and an organic layer formedbetween the first electrodes and the second electrode.

According to an aspect of the present invention, a decrease in thetransmittance of the second region where external light is transmittedmay be prevented as much as possible. Thus, a user may easily observeexternal images.

According to another aspect of the present invention, the transmissionwindows may be formed in the second electrode by using a simple method.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a schematic cross-sectional view of an organic light emittingdisplay device according to an embodiment of the present invention;

FIG. 2 is a schematic plan view of an organic light emitting displaydevice according to an embodiment of the present invention;

FIG. 3 is a schematic plan view of an organic light emitting displaydevice according to another embodiment of the present invention;

FIG. 4 is a cross-sectional view of a pixel of an organic light emittingdisplay device according to an embodiment of the present invention;

FIG. 5 is a plan view of a mask for forming a second electrode having atransmission window, according to an embodiment of the presentinvention;

FIGS. 6A through 6D are plan views illustrating an operation of forminga second electrode by using the mask illustrated in FIG. 5;

FIG. 7 is a plan view of a mask for forming a second electrode having atransmission window, according to an embodiment of the presentinvention;

FIG. 8 is a plan view of a mask for forming a second electrode having atransmission window, according to another embodiment of the presentinvention; and

FIG. 9 is a cross-sectional view of a pixel of an organic light emittingdisplay device according to another embodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

Here, it is to be understood that where is stated herein that one filmor layer is “formed on” or “disposed on” a second layer or film, thefirst layer or film may be formed or disposed directly on the secondlayer or film or there may be intervening layers or films between thefirst layer or film and the second layer or film. Further, as usedherein, the term “formed on” is used with the same meaning as “locatedon” or “disposed on” and is not meant to be limiting regarding anyparticular fabrication process.

FIG. 1 is a schematic cross-sectional view of an organic light emittingdisplay device according to an embodiment of the present invention.Referring to FIG. 1, the organic light emitting display device accordingto an embodiment of the present invention includes a substrate 1 and adisplay unit 2 placed on the substrate 1. External light enters theorganic light emitting display device via the display unit 2 and thesubstrate 1.

As will be described later, the display unit 2 transmits external light.Referring to FIG. 1, the display unit 2 allows a user positioned belowthe substrate 1 to view external images beyond the display unit 2.Although a bottom-emission type organic light emitting display device inwhich images on the display unit 2 are displayed toward the substrate 1as illustrated in FIG. 1, aspects of the present invention are notlimited thereto, and may be equally applied to a top-emission typeorganic light emitting display device in which images on the displayunit 2 are displayed in a direction opposite to the substrate 1.

FIG. 1 illustrates two adjacent pixels, namely, a first pixel P1 and asecond pixel P2, of the organic light emitting display device accordingto an aspect of the present invention.

Each of the first and second pixels P1 and P2 includes a first region 31and a second region 32.

An image is displayed on the display unit 2 in the first region 31, andexternal light passes through the display unit 2 in the second region32.

In other words, since each of the first and second pixels P1 and P2includes the first region 31 where images are displayed and the secondregion 32 which transmits external light, a user can see an externalimage through the second region 32 when the user does not see the imagedisplayed through the first region 31.

Thus, the second region 32 does not include devices such as a thin filmtransistor, a capacitor, and an organic light emitting device, and thusexternal light transmittance may be maximized and distortion of atransmitted image due to interference of the devices such as a thin filmtransistor, a capacitor, and an organic light emitting device may beprevented as much as possible.

FIG. 2 is a schematic plan view of a red pixel P_(r), a green pixelP_(g), and a blue pixel P_(b) that are adjacent to one another.

Each of the red, green, and blue pixels P_(r), P_(g), and P_(b) includesa circuit region 311 and an emission region 312 in the first region 31.The circuit region 311 and the emission region 312 are adjacent to eachother.

The second region 32 that transmits external light is adjacent to thefirst region 31.

As illustrated in FIG. 2, independent second regions 32 may be includedin the red, green, and blue pixels P_(r), P_(g), and P_(b),respectively. Alternatively, as illustrated in FIG. 3, second regions 32may be connected to one another across the red, green, and blue pixelsP_(r), P_(g), and P_(b). In the embodiment of FIG. 3, an area of thesecond region 32 through which external light passes is increased, andthus the transmittance of the entire display unit 2 may be increased.

Although the second regions 32 of the red, green, and blue pixels P_(r),P_(g), and P_(b) are integrally connected to one another in FIG. 3, theaspects of the present invention are not limited thereto, and the secondregions of only two adjacent pixels from among the red, green, and bluepixels P_(r), P_(g), and P_(b) may be connected to each other.

FIG. 4 illustrates a cross-section of the red, green, or blue pixel Pr,Pg, or Pb illustrated in FIGS. 2 and 3.

As illustrated in FIG. 4, a thin film transistor TR is arranged in thecircuit region 311. However, a pixel circuit including the thin filmtransistor TR may be also included in the circuit region 311.Alternatively, the circuit region 311 may further include a plurality ofthin film transistors TR and a storage capacitor. In this case, wiressuch as scan lines, data lines, and Vdd lines connected to the thin filmtransistors TR and the storage capacitor may be further included in thecircuit region 311.

An organic light emitting diode EL may be disposed in the emissionregion 312. The organic light emitting diode EL is electricallyconnected to the thin film transistor TR of the circuit region 311.

A buffer layer 211 is formed on the substrate 1, and a pixel circuitincluding the thin film transistor TR is formed on the buffer layer 211.

First, a semiconductor active layer 212 is formed on the buffer layer211.

The buffer layer 211 is formed of a transparent insulation material andprevents impurity elements from penetrating into the substrate 1 andplanarizes a surface of the substrate 1. The buffer layer 211 may beformed of any of various materials that can perform the functionsdescribed above. For example, the buffer layer 211 may be formed of aninorganic material such as silicon oxide, silicon nitride, siliconoxynitride, aluminum oxide, aluminum nitride, titanium oxide, ortitanium nitride, an organic material such as polyimide, polyester, oracryl, or stacks of these materials. The buffer layer 211 is not anessential element and may not be formed at all.

The semiconductor active layer 212 may be formed of polycrystal silicon,but is not limited thereto and may be formed of a semiconductor oxide.For example, the semiconductor active layer 212 may be a G-I-Z—O layer[a(In₂O₃)b(Ga₂O₃)c(ZnO) layer] (where a, b, and c are natural numbersthat respectively satisfy a≧0, b≧0, and c≧0). When the semiconductoractive layer 212 is formed of a semiconductor oxide, light transmittancein the circuit region 311 of the first region 31 may be increased, andthus external light transmittance of the entire display unit 2 may beincreased.

A gate insulating layer 213 is formed on the buffer layer 211 so as tocover the semiconductor active layer 212, and a gate electrode 214 isformed on the gate insulating layer 213.

An interlayer insulating layer 215 is formed on the gate insulatinglayer 213 so as to cover the gate electrode 214. A source electrode 216and a drain electrode 217 are formed on the interlayer insulating layer215 so as to contact the semiconductor active layer 212 via contactholes.

The structure of the thin film transistor TR is not limited to theabove-described structure, and the thin film transistor TR may havevarious other structures.

A passivation layer 218 is formed to cover the thin film transistor TR.The passivation layer 218 may be a single-layered or multi-layeredinsulating layer, an upper surface of which is planarized. Thepassivation layer 218 may be formed of an inorganic material and/or anorganic material.

As illustrated in FIG. 4, a first electrode 221 of an organic lightemitting diode EL electrically connected to the thin film transistor TRis formed on the passivation layer 218. The first electrode 221corresponds to each pixel.

An insulating layer 219 is formed of an organic and/or inorganicinsulating material on the passivation layer 218 to cover at least anedge portion of the first electrode 221.

The insulating layer 219 exposes only a central portion of the firstelectrode 221. Although the insulating layer 219 may be included tocover the first region 31, the first insulating layer 219 does notnecessarily cover the entire first region 31, and it is sufficient forthe insulating layer 219 to cover only a part of the first region 31,particularly, an edge of the first electrode 221.

An organic layer 223 and a second electrode 222 are sequentially stackedon the first electrode 221. The second electrode 222 covers the organiclayer 223 and the insulating layer 219, and second electrodes 222corresponding to all of the pixels are electrically connected to oneanother.

The organic layer 223 may be a low molecular weight organic layer or apolymer organic layer. When the organic layer 223 is a low molecularweight organic layer, the organic layer 223 may be formed by stacking ahole injection layer (HIL), a hole transport layer (HTL), an emissionlayer (EML), an electron transport layer (ETL), and an electroninjection layer (EIL) in a single structure or a composite structure,and may be formed of any of various materials such as copperphthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine(NPB), or tris-8-hydroxyquinoline aluminum (Alq3). The low-molecularweight organic layer may be formed by vacuum deposition. Herein, theHIL, the HTL, the ETL, and the EIL are common layers and may be commonlyapplied to red, green, and blue pixels.

The first electrode 221 may function as an anode, and the secondelectrode 222 may function as a cathode. Alternatively, the firstelectrode 221 may function as a cathode, and the second electrode 222may function as an anode.

According to an embodiment of the present invention, the first electrode221 may be a transparent electrode, and the second electrode 222 may bea reflection electrode. The first electrode 221 may include ITO, IZO,ZnO, In₂O₃, or the like each having a high work function. The secondelectrode 222 may be formed of a metal having a low work function, suchas Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, or Ca. Accordingly, theorganic light emitting diode EL is a bottom emission type in which lightis emitted towards the first electrode 221.

However, the aspects of the present invention are not limited thereto,and the second electrode 222 may also be a transparent type electrode.

The passivation layer 218, the gate insulating layer 213, the interlayerinsulating layer 215, and the insulating layer 219 may be transparentinsulating layers.

A sealing substrate 4 may be installed over the second electrode 222.The sealing substrate 4 is located outside the display unit 2 and bondedwith the substrate 1 by a sealant (not shown) so as to protect thesecond electrode 222 from external air. A filler (not shown) may befilled between the sealing substrate 4 and the second electrode 222, anda moisture absorbent may also be interposed therebetween. A sealingstructure for the display unit 2 is not limited to the use of thesealing substrate 4, and a film-shaped sealing structure may be used.

Transmission windows 224 are further formed in the second electrode 222and the insulating layer 219. The transmission windows 224 may be formedonly in the second electrode 222, or may be formed in at least oneselected from the group consisting of the passivation layer 218, theinterlayer insulating layer 215, the gate insulating layer 213, and thebuffer layer 211.

The transmission windows 224 are formed at locations corresponding tothe second regions 32. The transmission windows 224 may be formed in anypattern such as the one shown in FIGS. 2 and 3. However, it isunderstood that the transmission windows can have a different patternthan those illustrated in FIGS. 2 and 3.

However, it is difficult to form the transmission windows 224 in thesecond electrode 222, because a metal for the second electrode 222should be deposited using a mask having a shield portion correspondingto the pattern of the transmission windows 224 in order to form thetransmission windows 224 in the pattern and manufacturing the maskhaving the shield portion corresponding to the pattern is verydifficult.

A mask 5 illustrated in FIG. 5 is used to form the second electrode 222having the transmission windows 224 arranged in such pattern.

The mask 5 has an aperture 51 corresponding to a first region 31 of aspecific pixel. A pattern of the apertures 51 shown in FIG. 5 is used toform the transmission windows 224 having the pattern illustrated in FIG.3. The mask 5 has an aperture 51 corresponding to the first regions 31of three adjacent pixels, namely, a red pixel, a green pixel, and a bluepixel. The size of the aperture 51 is generally slightly greater thanthe overall size of the three pixels so that patterns obtained when amaterial used to form the second electrode 222 is deposited via theapertures 51 overlap each other. Thus, the second electrode 222 may actas a common electrode.

When the three pixels constitute a unit pixel, the apertures 51 areseparated from one another by a distance corresponding to the unit pixelin a horizontal direction and a vertical direction.

When a metal used to form the second electrode 222 is deposited on theorganic layer 223 by using the mask 5, a pattern illustrated in FIG. 6Ais obtained.

When the mask 5 is shifted by one unit pixel horizontally and then metalis deposited, a pattern as illustrated in FIG. 6B is obtained. When themask 5 is shifted again by one unit pixel downward and then metal isdeposited, a pattern as illustrated in FIG. 6C is obtained. Thereafter,when the mask 5 is shifted again by one unit pixel horizontally and thenmetal is deposited, a pattern as illustrated in FIG. 6D is obtained.Thus, as illustrated in FIG. 6D, the second electrode 222 having thetransmission windows 224 in the pattern of FIG. 3 is obtained.

The pattern of the apertures 51 of the mask 5 is not limited to thepattern illustrated in FIG. 5. In other words, if an aperture 51 isformed at the center of the four adjacent apertures 51 illustrated inFIG. 5 and the aperture 51 at the center is the same as each of the fouradjacent apertures 51, the second electrode 222 having the patternillustrated in FIG. 6D may be obtained by shifting the mask 5horizontally only once.

FIGS. 7 and 8 illustrate masks 5 having other shapes than the mask 5 ofFIG. 5.

An aperture 51 corresponding to a first region 31 corresponding to threepixels is formed around a region corresponding to a transmission window224. The pattern of the apertures 51 illustrated in FIG. 7 may allow thesecond electrode 222 having the pattern illustrated in FIG. 6D to beobtained by shifting the mask 5 horizontally only once. In this case,since an interval between apertures 51 is sufficient, the mask 5 is notdestroyed by a tensile force but may be stable.

FIG. 8 illustrates a modified example of FIG. 7. A center of an aperture51 protrudes upward and downward, and thus when a mask 5 of FIG. 7 isshifted horizontally by one unit pixel and deposition is performed,deposition occurs redundantly on the upward and downward protrusions ofthe aperture 51. Thus, the second electrode 222 may be stably formedthrough the entire display unit without any discontinuity.

The above embodiment applies not only to a structure in which a circuitpart including the thin film transistor TR is not overlapped by thefirst electrode 221 as illustrated in FIG. 4 but also to a structure inwhich a circuit part including the thin film transistor TR is overlappedby the first electrode 221 as illustrated in FIG. 9.

In the case of the structure illustrated in FIG. 9, when the firstelectrode 221 is formed as a reflection electrode, an effect where aconductive pattern of a circuit part is shielded by the first electrode221 may be obtained. Thus, distortion of a penetrated image due toexternal light scattered by the conductive pattern of the circuit partmay be suppressed.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1.-10. (canceled)
 11. A method of manufacturing an organic lightemitting display device, the method comprising: defining a plurality ofpixels on a substrate, each of the pixels comprising a first region thatemits light and a second region that transmits external light; forming aplurality of thin film transistors in the first region of each pixel;forming a plurality of first electrodes electrically connected to theplurality of thin film transistors, respectively, in the first region ofeach pixel; forming an organic layer on the plurality of firstelectrodes; and forming a second electrode on the organic layer by usinga mask having a pattern of apertures corresponding to the first region,wherein the second electrode comprises a plurality of transmissionwindows that correspond to the second regions.
 12. The method of claim11, wherein the apertures are separated from each other at regularintervals.
 13. The method of claim 12, wherein the apertures areseparated from each other at intervals smaller than or equal to adistance corresponding to at least one pixel. 14-17. (canceled)